1. Field of the Invention
The present invention relates to a method for controlling an X-ray diagnostic apparatus having a floor-mounted C-arm.
2. Description of the Related Art
Medical imaging diagnostic technology using X-ray diagnostic apparatus, MRI apparatus, or X-ray CT scanners has made rapid progress with the advance of computer technology, and has become indispensable for today's medical treatment.
In recent years, X-ray diagnosis has made a progress mainly in the field of circulatory. organs with the advance of catheterization. X-ray diagnostic apparatuses for circulatory organs generally include an X-ray generator, an X-ray detector, a support unit for the X-ray generator and the X-ray detector, a table (tabletop), an image processor, a display, and so on. The support unit turns, rotates, or moves a C-arm or Ω-arm around a patient (hereinafter, referred to as a subject) to allow radiography imaging in an optimum position or direction
An X-ray film or an image intensifier (II) has been used as X-ray detection element for use in the X-ray detector of X-ray diagnostic apparatuses. In the radiography imaging using the II, X-ray projection data (hereinafter, referred to as projection data) that is given by the passage of X-rays generated from an X-ray generator through the subject to an optical image by the II, and the optical image is converted to an electric signal by an X-ray TV camera, then converted from analog to digital data, and displayed on a monitor. Accordingly, the radiograph using the II allows real-time imaging which was impossible for that using a film, and also allows collection of digital projection data, thus allowing various image processing. As an alternative to the II, a two-dimensional-array plane detector has received attention, part of which has already come into practical use.
FIG. 9 shows a C-arm support unit used in a conventional circulatory-organ X-ray diagnostic apparatus. An X-ray generator 1101 is mounted to an end (the lower end) of a C-arm 1103 of the C-arm support unit 1110, while an X-ray detector 1102 having a plane detection element is mounted to the other end (the upper end) in such a manner as to face the X-ray generator 1101. The alternate long and short dash line 1108 in the drawing indicates an exposure axis connecting the focus of the X-ray tube in the X-ray generator 1101 and the center of the plane detection element of the X-ray detector 1102. The alternate long and short dash line indicates also the center line of a tabletop 1107 in a lateral reference position, or a base line BL for exposure which substantially agrees with the body axis of the subject.
The C-arm 1103 is retained by a stand 1105 installed on a floor 1106 through an arm holder 1104. The C-arm 1103 is mounted to an end of the arm holder 1104 slidably in the direction indicated by arrow a. The arm holder 1104 is mounted to the top of the stand 1105 in such a manner as to turn or rotate in the direction indicated by arrow b. The stand 1105 is composed of a stand fixing section 1105a fixed to the floor 1106 and a stand moving section 1105b that is rotatable in the direction of arrow c about the support axis.
The X-ray generator 1101 and the X-ray detector 1102 (hereinafter, collectively referred to as an imaging system) are set in a position and direction suitable for a subject (not shown) laid on the tabletop 1107 by the sliding of the C-arm 1103 in the direction a and the rotation of the arm holder 1104 in the direction b. Turning the stand moving section 1105b in the direction c enables the imaging system and the C-arm 1103 to be separated from the subject. The separation of the imaging system and the C-arm 1103 provides a working space for a doctor or a medical technologist (hereinafter, referred to as an operator) around the head of the subject, thus facilitating rearrangement of the subject on the tabletop 1107 or turn of the position before and after the examination, and placement of anesthetic equipment.
An L-shaped offset arm, as shown in FIG. 9, is generally used as the arm holder 1104. Forming the arm holder 1104 in L-shape enables the C-arm 1103 to be mounted on the side of the tabletop 1107, thus permitting the longitudinal end of the tabletop 1107 to be moved in the direction of arrow f to the vicinity of the stand 1105. In other words, the use of the L-shaped arm holder 1104 increases the moving range of the tabletop 1107, thereby increasing the subject distance. The use of the L-shaped arm holder 1104 also has the advantage of providing enough working space for the operator around the subject's head.
However, the provision of working space and increase of the subject distance by the rotation of the stand moving section 1105b or the L-shaped arm holder 1104 have limitation because the stand 1105 is fixed on the floor 1106, which is not always enough for the operator.
To solve the above problems, a ceiling-mounted C-arm support unit is proposed in which an arm holder is fixed to an end of an arm that is rotatably fixed at the other end to the ceiling, and in which the exposure region of the subject to can be set freely by bringing the rotation axis of the arm into agreement with the longitudinal center of the tabletop (for example, refer to JP-A-2000-70248).